The President of the High Council of the Time Lords is assassinated, and
the Doctor, newly returned to Gallifrey, is the prime suspect. But the
Doctor knows someone is framing him, and must rely on the help of the
reluctant Castellan Kelner to unveil a traitor in the High Council.
Ultimately, the trail leads to the dying, vengeful Master, who wishes to
harness the powers of Rassilon's greatest discovery, the mythical Eye of
Harmony. But to do so would mean the destruction of Gallifrey, and to
prevent this, the Doctor must risk his life in the surreal landscape of
the Matrix.

Production

With Elisabeth Sladen scheduled to leave Doctor Who two serials
into Season Fourteen, the thoughts of producer Philip Hinchcliffe and
script editor Robert Holmes turned to the creation of a new companion.
Neither had a clear vision of what this character should be like,
however, and they also had to contend with Tom Baker's desire that the
Doctor not be accompanied by other regular characters at all. Baker
thought that the Doctor should journey alone, talking to himself to
advance and explain the plot, rather than to a companion. Hinchcliffe
and Holmes finally acquiesced to Baker's lobbying and agreed not to
introduce a permanent companion immediately after Sarah's departure in
The Hand Of Fear. They felt that, if
nothing else, writers could invent surrogate “companions” to
assist the Doctor for a single adventure at a time.

It was agreed that the first of these solo-Doctor serials would be
authored by Holmes himself. Although the BBC usually discouraged script
editors from writing for their own programme, Holmes had received
special permission to do so for Doctor Who, following his
last-minute emergency rewrite of Pyramids Of
Mars the year before. Hinchcliffe suggested a storyline in the
vein of political conspiracy thrillers such as the paranoiac 1962 Frank
Sinatra film The Manchurian Candidate, in which the Doctor would
be framed as part of a sinister cover-up. Holmes decided that such an
adventure could best take place within the context of Time Lord society,
something that had been explored only superficially in Doctor Who
to date.

Instead of the suave, silky Time Lord played by Roger
Delgado, the new Master would be a desperate, skeletal creature

The Gallifreyan setting suggested to Hinchcliffe and Holmes that a
suitable villain for the piece would be the Doctor's Time Lord
archnemesis, the Master. The character had not been utilised since Frontier In Space in Season Ten. Although
plans had been mooted for a final adventure the next year which would
have killed the character off in a “blaze of glory”, actor
Roger Delgado was killed in a car crash before it could be made, and the
character had since lain dormant. By now, however, both Hinchcliffe and
Holmes were contemplating leaving Doctor Who at the end of the
season. Both felt that they had done as much with the show as they
could, and were developing a more adult science-fiction programme called
Lituvin 40 as their potential next assignment. As such, they
decided to reintroduce the Master in a transitional state, so that the
next production team would not be saddled with a version of the
character that they might not like. Instead of the suave, silky Time
Lord played by Delgado, the new Master would be a desperate, skeletal
creature barely clinging to life.

Holmes was working on Serial 4P -- initially called “The Dangerous
Assassin” and then The Deadly Assassin -- by April 1976,
although he was formally commissioned on May 27th. Since the story was
partly inspired by the conspiracy theories which had abounded after the
deaths of American personalities such as President John F Kennedy and
his brother Robert, Holmes included several subtle digs at the United
States. The Time Lord organisation which had occasionally been seen to
manipulate the Doctor in the past was christened the Celestial
Intervention Agency, sharing its initials with the Central Intelligence
Agency (often accused of being at the centre of various conspiracies).
The Doctor's line about “vaporisation without
representation” mocked a similar American slogan about taxation
that was popular during the War of Independence.

To this point, the Time Lords had been depicted in Doctor Who as
essentially godlike individuals. To fill in the details of their
culture, however, Holmes drew upon the fact that Gallifrey had been seen
to produce so many renegades -- not just the Doctor amd the Master, but
also the Meddling Monk (from The Time
Meddler), the War Chief (from The War
Games), Omega (from The Three
Doctors) and Morbius (from The Brain Of
Morbius). He decided to show that the Time Lords' previous
manifestations masked a decaying, corrupt and stagnant civilisation. In
so doing, Holmes created many of the concepts which would become
hallmarks of Doctor Who's mythology, including Rassilon (the
founder of Gallifreyan society), the Eye of Harmony, the Panopticon, the
Matrix, the Prydonian chapter, artron energy, and the notion that Time
Lords are limited to only twelve regenerations.

Robert Holmes created hallmarks of Doctor Who mythology, including Rassilon and the
idea that Time Lords can only regenerate 12 times

The director assigned to The Deadly Assassin was David Maloney,
whose last Doctor Who work had been on Planet Of Evil a year earlier. Maloney worked
closely with designer Roger Murray-Leach and costume designer James
Acheson to give Gallifrey a consistent, cohesive look. Although he would
eventually be replaced on the serial by Joan Ellacott, Acheson
contributed the Time Lords' distinctive high-collared apparel, while
Murray-Leach reused a symbol he had designed for Season Twelve's Revenge Of The Cybermen as the Prydonian seal.
Both would become enduring elements of Gallifrey's portrayal in
Doctor Who, with the latter subsequently coming to be known as
the “Seal of Rassilon”.

Eager to take Doctor Who into virgin territory, Hinchcliffe had
requested that Holmes write one episode of The Deadly Assassin as
a surrealist nightmare, to be captured entirely on film. This inspired
the extended duel between the Doctor and Chancellor Goth within the
confines of the Matrix, which formed the lion's share of the third
installment and consumed the entirety of the serial's location filming.
This began at Betchworth Quarry in Betchworth, Surrey, where material on
the plains and in the wasteland was completed from July 26th to
28th.

On the last day, cast and crew moved to the Royal Alexandra and Albert
School in Merstham, Surrey. Sequences in the jungle environment were
recorded there through the 30th. Because the pond water was too murky,
the shot of Goth trying to drown the Doctor was actually performed in
the school's swimming pool. Work on July 30th concluded with the scene
of the biplane attack, captured at Wycombe Air Park in High Wycombe,
Buckinghamshire. This locale was a late substitution for the planned
venue, the Redhill Aerodrome in Redhill, Surrey.

The first studio session for The Deadly Assassin took place from
August 15th to 17th in BBC Television Centre Studio 3. For the role of
the Master, Maloney had cast Peter Pratt, a skilled voice artiste and
opera performer who had been a friend of Delgado's. Pratt's other
television credits included Z Cars and Play For Today;
this would be his only Doctor Who appearance prior to his death
on January 11th, 1995. The first studio block principally dealt with
episodes one and two, beginning with scenes in the TARDIS, the museum,
and the cloisters on August 15th. The next day took in material in the
chancellery, the lift and the Panopticon, including the climactic fight
in part four. The 17th involved the completion of the remaining
Panopticon scenes, as well as those in the service gallery and the
records room.

A humorous title card at the end of episode four would
have thanked the High Court of Time Lords for their co-operation

The second studio session was originally scheduled for August 30th and
31st, but was shifted to the 1st and 2nd of September. It was held in
TC8, and was largely devoted to episodes three and four. September 1st
saw the recording of the remaining records room material, as well
as sequences set in the detention cell (from episode two) and the
Master's sanctuary, which included scenes from the first two
installments. The final studio day saw recording on the sets for the
chancellery, the vault, the chimney, and the museum, the latter
including a remount of the arrival of the TARDIS for part one.

At one point, it was planned to include a humorous title card at the end
of episode four reading, “We thank the High Court of Time Lords
and the Keeper of the Records for their help and co-operation”.
Ultimately, however, it was decided that this lampooned the production
too much, and it was removed. The transmission of part three on November
13th proved to be far less of a laughing matter, as it saw Doctor
Who once again come under fire from Mary Whitehouse and her National
Viewers And Listeners Association. Whitehouse had attacked the programme
on several occasions before, but never with such venom and conviction as
she reserved for this particular broadcast.

Most significantly, Whitehouse roundly condemned the extended
freeze-frame of the Doctor's head being held beneath the water which
closed the episode, even quoting one child who had allegedly told his
mother that he would do the same to his younger brother the next time
the boy angered him. Unlike past complaints by Whitehouse's
organisation, on this occasion the NVALA was successful in cajoling an
apology from BBC Director General Sir Charles Curran. Indeed, the BBC
even went so far as to edit the master tape of The Deadly
Assassin part three to expunge the offending sequence altogether.
Consequently, the BBC no longer holds a complete copy of the episode.
Fortunately, it has been reconstructed using the analogous material from
the serial's final installment.